The present invention relates to a control unit for the synchronization of a film projector with a tape recorder which enables the user to readily and automatically skip forward or skip backward one or more frames at will. Projector and recorder units are well known in audio visual education, generally utilizing 35mm slides or film strips and phonograph records or magnetic tape units including the reel-to-reel, cassette and magazine recorders. Projector-recorder units are quite versatile and have been used in all levels of educational institutions, for a variety of commercial, industrial and community purposes as well as for entertainment.
Notwithstanding the universal employment of projector-recorder units and the ready availability of equipment, most existing systems are designed to function only in a forward direction and one frame at a time. The user cannot readily replay or skip ahead several frames, nor can he stop and hold at a desired frame without having to re-synchronize the audio portion of the program, which is not only time consuming, but also tedious.
In general, there are two categories of projector-recorder systems currently available. The first and most rudimentary of the two is the slave system. Characteristically nonreversible, the projector or the operator advances slides or frames in response to a command signal from the audio equipment. The inconvenience arises when it becomes necessary or at least desirable to replay previously viewed frames. The second system, a sound-on-slide projector-recorder, eliminates the deficiency of the first system by placing the pre-recorded narration directly on the corresponding slide. However, narration time is necessarily restricted to approximately 30 seconds due to the limited amount of space on each slide.